Yo yo! Thanks for the question William.
My thoughts in a nutshell:
1. People buy on emotions and justify those purchases with logic
2. The story behind the product/team creates empathy, trust, feelings around the product, and expected feelings when someone "owns" the product.
3. There are different types of buyers. Some buyers are more emotional than others. Some more more rational. Some will love your story. Other will get sucked into how they can use the product. The sales page is there to appeal to all types. Some might just watch the vid. Others will look more into the product photos and text.
4. The copywriting and communication that you do PRIOR to them viewing the page also impacts this. If someone is coming from your email list, maybe they already have an idea of the story or problem, so they're just watching the vid to see the finished product. If it's cold traffic, they might be experiencing your product for the first time. If it's PR traffic, they might be impressed with a certain aspect.
What I usually do when I'm looking into a campaign:
1. Look at funding progress and time left.
2. Look at the images to see what the product is.
3. Read a paragraph or two of the story or founder.
4. Take the time to watch the video.
I'm weird tho :-p. I also am looking for different things because I'm also thinking how I can use the campaign or if I can bring them on the podcast:
http://www.crowdcrux.com/itunesSal